Terminal bushing



May 16, 1933.

M MORRISON 1,908,779

TERMINAL BUSHING Filed Aug. 22, 1931 Iliff/VIII# f ATTO Y Patented May 16, 1933 UNITED STATES PATENT OFFICE MONTFORD MORRISON, OFIMONTCLAIR, NEW' JERSEY, ASSIGNOR TO WESTINGHOUSE X-RAY COMPANY, INC., A CORPORATION OF DELAWARE TERMINAL BUSHING .Application led August 22, 1931.

My invention relates to high tension insulating bushings and has particular reference to insulating bushings of the general type commonly utilized for conducting the high tension current from an encased oil immersed source of high potential electrical energy to the exterior thereof.

Various types of insulating bushings are well known to the art which are usually constructed of ceramic material having a high dielectric strength but these devices are fragile and costly to construct.

It is an object of my invention to provide a high tension insulating bushing having a high dielectric strength and which is economical to manufacture.

Another object of my invention is to provide a high tension insulating bushing which will withstand corona effects and all electrical stresses to which the insulator may be subjected.

Still further objects of my invention will become apparent by reference to the accompanying drawing wherein the single igure illustrates an elevational view in section of my high tension insulating bushing.

Referring now to the drawing in detail l have shown in the figure a casing 5 adapted to surround a high tension source of electric energy such as a transformer (not shown). An oil tight cover plate 6 is arranged to be firmly secured to the casing 5 and an insulating and cooling material, such as oil 7, is arranged to immerse the hi h tension source.

A metallic annular ring 8 1s rigidly secured to the cover plate 6 by suitable means, such as rivets or bolts 9.

A metallic conductor 10 is concentrically disposed within the opening of the annular ring 8 and is in turn surrounded by an insulating material 12 of hi h dielectric strength, but which is deleterious y afected by contact with oil.

This material 12 may be of a mixture, such as resin, beeswax and parafline or other ana logous substances having the desired dielectric strength. The metallic conductor 10 and insulating material 12 extends a substantial distance above and below the annular ring 8 and at its lower extremity is arranged to Serial No. 558,678.4

protrude into the cooling and insulating medium, such as the oil 7.

The composition of the aforementioned insulating material being deleteriously affected by contact with the oil is, therefore, prevented from actual contact therewith by a second high tension insulating material, such as varnishedcambric, paper or a phenolic condensation product 13 having a high dielectric strength. This latter insulating material 13 is wound in the form of spirally successive layers which increase in diameter toward the annular ring 8 at which point the electric stresses are greatest due to the close proximity of the high tension metallic conductor 10 `to the annular ring 8 which is in common practice usually grounded.

The insulating material-13 at the point 14 extends a substantial distance longitudinally of the insulating material 12. The diameter at this point is of such dimensions as to fit tightly within the annular ring 8 and serves to support the insulator within the cover plate 6.

lln order to make the entire insulator of uniform diameter which corresponds to the internal diameter of the annular ring 8 the insulating material 12 is of slightly less diameter over that portion in which the wrapped insulating material 13 is superimposed in order that the combined insulating materials equal the interior diameter of the annular ring 8, and the diameter of the insulating material 12. The insulating material 13 is provided with a portion 15 immediately above the annular ring 8 of an increased diameter than the remaining portions of the insulator which, together with the tightness of the insulator in passing through the annular ring, assists in support ing the entire insulator within the cover plate. The metallic conductor 10 is threaded at both of its extremities and suitable washers 16 and nuts 17 are arranged to hold the metallic conductor firmly within the insulator and for the purposes of connecting the respective lead wires to the insulator.

A petticoat portion 18 is provided at the upper extremity of the insulator for the purpose of protecting the insulator from cli- 10( matic conditions when the same is used in outdoor construction.

My insulator may be molded of the material which is deleteriously aected by the oil and then wra ped with the material which is unaifecte by the oil. This latter material may be applied after the insulator has been ositioned within the cover plate and if desired the material 13 may be dipped in an oil resisting compound to increase the resistance of the material, or this dip ing may be dispensed with, if desired, by se ecting the proper insulating material.

t can, therefore, be readily1 seen that I have constructed a high tension insulating bushing which has a high electric strength and in which the greater portion thereof may be constructed o a non-oil resisting compound and a portion thereof covered with an oil resisting insulating material to prevent the insulator from actually contacting the oil immersing the high tension source.

By selecting materials that are deleteriously affected by contact with oil but which have a higher dielectric strength than the usual materials employed, which are unaffected b contact with the oil, such as ceramic materia and covering a ortion of the same by an oil resisting insu ating material, my entire insulator can be more economically manufactured than those of the prior art.

Although I have shown and described one specific embodiment of m invention I do not desire to be limited t ereto as various other modifications of the same may be made without departing from the spirit and scope of the invention as set forth in the appended claims. v

What is claimed is:

1. In combination with a casing for an oil immersed high tension source, a high tension insulating bushing comprising a high ten sion conductor, a high tension insulating material deleteriously affected by oil surrounding said conductor and a high tension insulating material unaffected by contact with oil, s irally wound about one extremity of said rst mentioned insulating material and in contact with the oil immersing said high tension source to prevent the deleteriously affected insulating material from contacting the oil immersing said high tension source.

2. In combination with a casing for an oil immersed high tension source, a high tension insulating bushing comprising a high tension conductor, a nonoil resisting high tension insulating material having a dielectric strength greater than oil resistin insulating material surrounding said con uctor, and a high tension oil resisting insulating material superim osed in successive layers upon a portion o said first mentioned insulatingmaterial and in contact with the oil immersing said high tension source to prevent the nonfoil insulating material from contacting the oil immersmg said high tension source. 3. In'combination with a casing for an oil immersed h' h tension source, an oil ti ht cover plate or said casing, a high tension insulating bushing secured to said cover plate an extend above and below the same, compr' a igh tension conductor, a non-oil resisting high tension insulat' material having a hi h dielectric stren surroundiililg said con uctor and extendi substantia y the entire length thereof, an an oil resisting high tension insulat' material s irally wound in successive ayers about e portion of said first mentioned insulating material `dispod below said oover plate and in contact with the oil immersing said high tension source.' c 4. In combination with a casing for an oil immersed high tension source, a high tension insulating bushing comprising a high tension conductor, a hi h tension insulatin material having a hi dielectric st and deleteriously aected by oil surrounding said conductor, and a high tension insulating material unaffected by oil wound in successive layers upon a portion of said irst mentioned insulating material to prevent the same from contacting the oil immersing said high tension source.

5. In combination with a cas' for an oil immersed high tension source, a h tension insulating bushing comprising a igh tension con uctor, a high tension insulat material ha a high dielectric strengt and deleterio y affected by oil surroundin saidnductor, and a h tension insu ating material unaffected y oil spirally wound in successive layers upon a portion of said first mentioned insulating material to increase the diameter of said last mentioned insulating material upon application of each successive layer until a maximum is reached at the point where the electrostatic 'stress is greatest and said last mentioned insulating material being in contact with the oil immersing said high tension source.

In testimony whereof, I have hereunto subscribed my name this 17th day of August, 1931.

. MONTFORD MORRISON. 

